Vehicles are equipped with a Heating, Ventilation and Air Conditioning (HVAC) System for controlling indoor temperature and creating a pleasant indoor environment.
Recently, a Full Automatic Temperature Control (FATC) system is being applied to most vehicles in order to maintain a pleasant environment by automatically controlling the indoor temperature in accordance with the temperature set by a driver or a passenger.
In the FATC system, when a user sets the temperature, an air conditioning controller receives detection signals of sensors such as a solar radiation sensor for detecting the solar radiation, an external temperature sensor for detecting the external temperature and an in-vehicle temperature sensor for detecting the indoor temperature, and calculates the thermal load of the indoor based on the detected values of each sensor in order to control the indoor temperature. In consideration of the air conditioning load corresponding thereto, the discharge mode, the discharge temperature, the discharge direction, and the discharge air volume are determined.
Furthermore, in order to control the indoor temperature and the system operation, the air conditioning controller receives detected values of a discharge temperature sensor for detecting the discharge temperature, a heater temperature sensor for detecting the temperature of an electric heater (e.g., PTC heater; used as an auxiliary heater in case of internal combustion engine, and used as a main heater in case of electric vehicle), and an evaporator temperature sensor for detecting the temperature of an evaporator, and controls the operation elements such as an indoor/outdoor air door (intake door) actuator, a temperature control door (temp. door) actuator, a wind direction control door (mode door) actuator, a dehumidification (defog door) actuator, an air conditioning blower, a compressor, and an electric heater.
Meanwhile, in order to control the wind direction, temperature, and air volume in a vehicle, a plurality of doors such as an indoor/outdoor air door determining the inflow of indoor/outdoor air, a temperature control door (temp. door) determining the flow rate passing through a heater core and the flow rate bypassing the heater core, a wind direction control door (mode door) determining modes such as face, floor, mix, and bi-level, and a dehumidification door are installed in the HVAC system.
Also, as air conditioning actuators, door actuators for the opening/closing and movement of the doors are installed in each door. Basically, the door actuator includes a motor generating a torque.
More specifically, as shown in FIG. 1, a door actuator 10 includes a motor 11 equipped with a worm gear 12 on the shaft thereof, reduction gears 13 engaging with the worm gear 12 and delivering a reduced torque, an output gear 14 engaging with the reduction gears 13 and outputting the torque, a feedback sensor 15 outputting a voltage generated by a variable resistor in accordance with the rotation of the output gear 14 to feedback the voltage to a controller (not shown), and a case 16 mounted with the foregoing components.
As prior art documents about the door actuator, there are Korean Utility Model Nos. 20-1310310 (Mar. 31, 2003), 20-0397378 (Sep. 26, 2005), 20-0459626 (Mar. 28, 2012) and Korean Patent No. 10-0828838 (May 2, 2008).
A voltage signal outputted from the feedback sensor 15 is used as a feedback signal for controlling the location (location of motor) of the actuator 10. When a target location of the actuator corresponding to a desire location of the door is determined and a target feedback value (feedback voltage) according thereto is determined, the door actuator (motor) is controlled in a direction where the feedback value increases when the feedback value by the feedback sensor is smaller than the target feedback value, and the door actuator (motor) is controlled in a direction where the feedback value decreases when the feedback value by the feedback sensor is larger than the target feedback value.
FIGS. 2 and 3 are views illustrating a circuit connection state of a feedback sensor. The feedback voltage varied by a variable resistor 15a in accordance with the rotation (corresponding to the location of motor) of the output gear (not shown) upon normal/reverse rotation of a motor 11 is outputted from a feedback sensor 15.
Meanwhile, a technology of sensing the abnormality of the motor such as motor stall is being applied using a signal value (feedback value) of a feedback sensor in an air conditioning actuator.
An air conditioning controller (not shown) monitors the change of the feedback value that is a voltage value outputted from the feedback sensor, i.e., feedback value generated in accordance with the rotation location of the motor in a state where the driving of the motor is controlled in order to sensor the motor stall.
In this case, when there is no change for a certain time by measuring time from a time point where there is no change in the feedback value, the motor is determined as stalled.
However, there is a limitation in that time is spent to verify whether or not there occurs a change of the feedback value.
Accordingly, a method of recognizing the motor stall upon change of the current pattern by receiving a current value may be used in order to reduce the sensing time.
That is, as shown in FIG. 4, a shunt resistor 31 that is a resistor for current sensing is connected in series to the motor 11, and a current sensing circuit unit 32 capable of sensing a current flowing through the shunt resistor 31 is provided.
The current sensing circuit unit 32 is configured to output a current signal corresponding to voltages value at both ends of the shunt resistor 31. The air conditioning controller (not shown) receives the current signal from the current sensing circuit unit 32, and recognizes the motor stall when the current pattern changes.
FIG. 5 is a view illustrating a change of the current pattern generated upon motor stall in the method using the shunt resistor 31, which shows a current change section upon stall of the motor in addition to an initial operation current section and a normal operation current section upon operation of the motor.
Accordingly, the motor may be determined as stalled when a current of a reference level or more is sensed through the current sensing circuit unit 32.
However, a plurality of doors, such as an indoor/outdoor air door determining the inflow of indoor/outdoor air, an individual temperature control door (temp. door; driver's side and passenger's side) for controlling the respective seats, a wind direction control door (mode door) determining modes such as face, floor, mix, and bi-level, and a dehumidification door, are installed in the HVAC system.
Accordingly, since actuators for each door need to be provided in addition to actuators for rotating two doors together, it should be individually diagnosed and sensed whether or not each motor of actuators is stalled.
In this case, in the method of using a shunt resistor for each actuator, the shunt resistor for current sensing usually has a very small resistance value of several tens or hundreds of mΩ. In order to reduce a power loss due to the shunt resistor, it is advantageous that the shunt resistor has a small resistance value.
However, when the shunt resistor is installed for each motor, a power loss (including power loss due to the shunt resistors individually installed) of I2R occurs due to the current (I) and the resistance (R). Also, when the resistance values of the shunt resistors are different, an error may occur in measurement of the current value.
Particularly, since the motor driver 20 and the motor 11 are generally connected through wiring and the resistance component of the wire may reach several ohms (Ω) in accordance with the air conditioning actuator, a significant error may occur due to a large deviation (including a resistance deviation of the shunt resistor) in the method of measuring voltages at both ends of the shunt resistor.
Thus, it is very difficult to implement a logic for determining the motor stall from the voltages at both ends of the shut resistor by a controller. Also, since there is a limitation in that an error needs to be adjusted one by one for each vehicle model, it is actually impossible to apply to the controller.
Accordingly, even if a certain time is taken to sense the motor stall, the method of using a signal of the feedback sensor described above is being applied.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.